1. Field of the Invention
The present invention relates to a magnetic head which is satisfactory in the anti-corrosion characteristic and the input and output characteristic, and is sufficiently durable against cracking in a base thereof; a method for producing the magnetic head; a video recording and reproduction apparatus including the magnetic head, and a video camera including the magnetic head.
2. Description of the Related Art
As a magnetic head for VCRs or the like, a ferrite head including a magnetic core formed by combining a pair of ferrite sections together is conventionally used. Recently, in accordance with the improvement in the magnetic recording density, a metal-in-gap head (MIG head) has become often used. The MIG head uses a metal magnetic material having a more highly saturated magnetic flux density than that of ferrite for a portion in the vicinity of a recording/reproduction gap.
FIG. 8 schematically shows an exemplary conventional ferrite head 300. FIGS 9A through 9D schematically show an exemplary conventional MIG head 400.
With reference to FIG. 8, the ferrite head 300 includes a pair of ferrite sections F1A and F1B, and a nonmagnetic layer N1 and glass bonding sections G1 both provided between the pair of ferrite sections F1A and F1B for combining the ferrite sections F1A and F1B.
With reference to FIGS. 9A through 9D, the MIG head 400 includes a pair of magnetic core halves MCA and MCB, and a nonmagnetic layer N2 and glass bonding sections G2 both provided between the pair of magnetic core halves MCA and MCB for combining the magnetic core halves MCA and MCB. The magnetic core half MCA includes a ferrite section F2A, at least one underlying layer (not shown) provided on the ferrite section F2A, and a metal magnetic thin film FM2 provided between the underlying layer and the nonmagnetic layer N2. The magnetic core half MCB includes a ferrite section F2B, at least one underlying layer (not shown) provided on the ferrite section F2B, and a metal magnetic thin film FM2 provided between the underlying layer and the nonmagnetic layer N2.
As a material for the metal magnetic thin films FM2, amorphous materials (e.g., Japanese Laid-Open Publication No. 63-120653), Fexe2x80x94N-based materials, and Fexe2x80x94C-based materials have been developed. The Fexe2x80x94N-based materials and Fexe2x80x94C-based materials are obtained by thermally treating an amorphous film mainly containing Fe to deposit microscopic crystals having a diameter of about 5 to about 20 nm (e.g., Hasegawa, Journal of the Magnetics Society of Japan, 14, pp. 319-322 (1990); and Nago, IEEE, Trans., Magn., Vol, 28, No. 5 (1992)).
Among these materials, materials obtained by depositing or growing microscopic crystalline particles having a magnetic metal composition and thus having a highly saturated magnetic flux density of 1.2 T or higher and a soft magnetic characteristic need to be improved in the anti-corrosion characteristic.
For this purpose, attempts have been made to add light elements having passivity to these materials. However, the light elements, which easily react with oxygen, nitrogen and the like, react with oxygen used for making crystals amorphous or microscopic and thus tend not to remain in the microscopic crystalline particles having the magnetic metal composition.
In order to overcome this problem, in addition to adding the light elements having passivity to the above-mentioned metal magnetic materials, the magnetic crystalline particles of these materials are each controlled to have a relatively large size and a relatively large surface area. The metal magnetic thin film thus developed has satisfactory magnetic characteristics, a highly saturated magnetic flux density, and a sufficient anti-corrosion characteristic (e.g., Japanese Laid-Open Publication No. 10-223435).
An MIG head is a composite device of ferrite, which is an oxide, and a metal magnetic thin film. Accordingly, the MIG head involves the problems that the ferrite base may be cracked by an internal stress generated in the metal magnetic thin film and that the magnetic characteristics may be deteriorated by a reaction at the interface between the ferrite base and the metal magnetic thin film. The above-mentioned problems are caused by the structure of the MIG head or the material characteristics of the metal magnetic thin film.
An optimum structure of a magnetic head varies in accordance with the material characteristics of the metal magnetic thin film. In order to improve the characteristics of the magnetic head, it is necessary to solve the problems of the cracks in the ferrite base and the deterioration of the magnetic characteristics as well as to improve the materials design.
According to one aspect of the invention, a magnetic head includes a pair of magnetic core halves; and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves. The pair of magnetic core halves each includes an oxide magnetic base, at least one underlying layer provided on the oxide magnetic base, and a metal magnetic thin film provided between the underlying film and the nonmagnetic layer. The metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa greater than about 4.84 Va⅔. At least one of the pair of magnetic core halves has a winding window therein. The metal magnetic thin film is provided in such a manner as to prevent the oxide magnetic base from cracking due to an internal stress generated in the metal magnetic thin film.
In one embodiment of the invention, the metal magnetic thin film includes magnetic crystalline particles, which have an average length of a longer side of more than about 50 nm.
In one embodiment of the invention, the magnetic crystalline particles have at least one shape selected from the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape including the magnetic crystalline particles of the generally needle-like shape and the generally column-like shape; and the magnetic crystalline particles having the generally needle-like shape and the generally column-like shape have an average length of a shorter side of more than about 5 nm and less than about 60 nm.
In one embodiment of the invention, where dS is an average length of a shorter side of the magnetic crystalline particles and dL is an average length of a longer side of the magnetic crystalline particles, 5 nm less than dS less than 60 nm and 60 nm less than dL less than 5000 nm.
In one embodiment of the invention, the metal magnetic thin film has a composition represented by (MaXbZc)100-dAd, where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni; X includes at least one element selected from the group consisting of Si, Al, Ga and Ge; Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr; A includes at least one element selected from the group consisting of O and N; and a, b, c and d fulfill the relationships of about 0.1xe2x89xa6bxe2x89xa6about 26, about 0.1xe2x89xa6cxe2x89xa6about 5, a+b+c=100, and about 1xe2x89xa6dxe2x89xa6about 10.
In one embodiment of the invention, the pair of magnetic core halves each have a combining surface which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, a recording medium running surface on which a recording medium runs, and outer side surfaces continuous from the combining surface and from the recording medium running surface; and the metal magnetic thin film is not provided on the outer side surfaces.
In one embodiment of the invention, the metal magnetic thin film has a composition represented by (FeaSibAlcTd)100-eNe where T includes at least one element selected from the group consisting of Ti and Ta; and a, b, c, d and e fulfill the relationships of about 10xe2x89xa6bxe2x89xa6about 23, about 0.1xe2x89xa6dxe2x89xa6about 5, about 0.1xe2x89xa6c+dxe2x89xa6about 8, a+b+c+d=100, and about 1xe2x89xa6exe2x89xa6about 10.
In one embodiment of the invention, Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va and Cr.
In one embodiment of the invention, X includes at least one element selected from the group consisting of Si and Ge; and a, b, c and d fulfill the relationships of about 0.1xe2x89xa6bxe2x89xa6about 23, about 0.1xe2x89xa6cxe2x89xa6about 8, a+b+c=100, and about 1xe2x89xa6dxe2x89xa6about 10.
In one embodiment of the invention, the metal magnetic thin film has a composition represented by (FeaSibAlcTd)100-e-fNeOf where a, b, c, d, e and f fulfill the relationships of about 10xe2x89xa6bxe2x89xa6about 23, about 0.1xe2x89xa6dxe2x89xa6about 5, about 0.1xe2x89xa6c+dxe2x89xa6about 8, a+b+c+d=100, and about 1xe2x89xa6e+fxe2x89xa6about 10, and 0.1xe2x89xa6fxe2x89xa6about 5.
In one embodiment of the invention, the at least one underlying layer contains at least one of an oxide of Al, and oxide of Si, a nitride of Al, a nitride of Si, and a mixture thereof.
In one embodiment of the invention, the at least one underlying layer includes a first underlying layer in contact with the magnetic core half and a second underlying layer in contact with the metal magnetic thin film. The first underlying layer contains at least one of an oxide of Al, and oxide of Si, a nitride of Al, a nitride of Si, and a mixture thereof. The metal magnetic thin film contains at least one of oxygen and nitrogen; and the second underlying layer contains an element which is a main component of the metal magnetic thin film, and at least one of oxygen and nitrogen in a larger amount than the amount contained in the metal magnetic thin film. The second underlying layer contains crystalline particles. The crystalline particles have an average particle diameter of about 5 nm or less at least in the vicinity of an interface between the first underlying layer and the second underlying layer.
In one embodiment of the invention, the first underlying layer contains an oxide of Al, and has a thickness of about 0.5 nm or more and about 4 nm or less. The second underlying layer has a thickness of about 0.5 nm or more and about 200 nm or less.
In one embodiment of the invention, the oxide magnetic base of each of the magnetic core halves contains a ferrite single crystal. The ferrite single crystal has a combining surface corresponding to a combining surface of the magnetic core half which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, and a recording medium running surface on which a recording medium runs.
In one embodiment of the invention, the ferrite single crystal includes an MnZn ferrite single crystal containing A mol % of Fe2O3, B mol % of MnO and C mol % of ZnO, where A, B and C fulfill the relationships of about 52xe2x89xa6Axe2x89xa6about 57, about 5xe2x89xa6Bxe2x89xa6about 29, and about 16xe2x89xa6Cxe2x89xa6about 21.
In one embodiment of the invention, the pair of magnetic core halves each have a combining surface which is combined with the other magnetic core half with the nonmagnetic layer interposed therebetween, and a recording medium running surface on which a recording medium runs. At least one of the pair of magnetic core halves has a bottom surface and a first inner side surface for forming the winding window. The first inner side surface extends from the bottom surface toward the combining surface and is provided on the side of the recording medium running surface with respect to the bottom surface. An angle made by the first inner side surface and the combining surface is about 22.5xc2x0 or more and about 70xc2x0 or less.
In one embodiment of the invention, the winding window is provided in one of the pair of magnetic core halves, and the angle made by the first inner side surface and the combining surface is about 45xc2x0 or more and about 70xc2x0 or less.
In one embodiment of the invention, the winding window is provided in both of the pair of magnetic core halves, and the angle made by the first inner side surface and the combining surface is about 22.5xc2x0 or more and about 50xc2x0 or less.
In one embodiment of the invention, the first inner side surface includes a second inner side surface adjacent to the combining surface and a third inner side surface adjacent to the bottom surface. An angle made by the second inner side surface and the combining surface is about 22.5xc2x0 or more and about 70xc2x0 or less. An angle made by the third inner side surface and the bottom surface is about 90xc2x0.
In one embodiment of the invention, the winding window is provided in one of the pair of magnetic core halves, and the angle made by the second inner side surface and the combining surface is about 45xc2x0 or more and about 70xc2x0 or less.
In one embodiment of the invention, the winding window is provided in both of the pair of magnetic core halves, and the angle made by the second inner side surface and the combining surface is about 22.5xc2x0 or more and about 50xc2x0 or less.
In one embodiment of the invention, the metal magnetic thin film has a composition represented by (FeaSibAlcTid)100-e-fNeOf, where a, b, c, d, e and f fulfill the relationships of about 10xe2x89xa6bxe2x89xa6about 13, about 1xe2x89xa6cxe2x89xa6about 3, about 1xe2x89xa6dxe2x89xa6about 3, a+b+c+d=100, about 4xe2x89xa6e+fxe2x89xa6about 10, and about 0.1xe2x89xa6fxe2x89xa6about 2.
In one embodiment of the invention, the oxide magnetic base of each of the magnetic core halves has a combining surface which is combined with the oxide magnetic base of the other magnetic core half with the nonmagnetic layer interposed therebetween, and side surfaces continuous from the combining surface. An angle made by the combining surface and each of the side surfaces is about 70xc2x0 ore more and about 90xc2x0 or less. The metal magnetic thin film is provided on the combining surface but is not provided on the side surfaces.
According to another aspect of the invention, a method for producing a magnetic head is provided. The magnetic head includes a pair of magnetic core halves, and a nonmagnetic layer provided between the pair of magnetic core halves for combining the pair of magnetic core halves. The pair of magnetic core halves each include an oxide magnetic base, at least one underlying layer provided on the oxide magnetic base, and a metal magnetic thin film provided between the underlying layer and the nonmagnetic layer. The metal magnetic thin film includes a magnetic film containing, as a major material, magnetic crystalline particles having an average volume Va and an average surface area Sa fulfilling the relationship of Sa greater than about 4.84 Va⅔. At least one of the pair of magnetic core halves has a winding window therein, and the metal magnetic thin film is provided in such a manner as to prevent the oxide magnetic base from cracking due to an internal stress generated in the metal magnetic thin film; wherein the metal magnetic thin film has a composition represented by (MaXbZc)100-dAd, where M includes at least one magnetic metal element selected from the group consisting of Fe, Co and Ni, X includes at least one element selected from the group consisting of Si, Al, Ga and Ge, Z includes at least one element selected from the group consisting of elements of group IVa, elements of group Va, Al, Ga and Cr, and A includes at least one element selected from the group consisting of O and N, and a, b, c and d fulfill the relationships of about 0.1xe2x89xa6bxe2x89xa6about 26, about 0.1xe2x89xa6cxe2x89xa6about 5, a+b+c=100, and about 1xe2x89xa6dxe2x89xa6about 10. The metal magnetic thin film includes magnetic crystalline particles, the magnetic crystalline particles have at least one shape selected from the group consisting of a generally needle-like shape, a generally column-like shape, and a multiple-branch shape combining the generally needle-like shape and the generally column-like shape; and the magnetic crystalline particles have an average length dS of a shorter side of about 5 nm less than dS less than about 60 nm and an average length of a longer side of about 60 nm less than dL less than about 5000 nm. The method includes a winding window formation step of forming a winding window in at least one of a pair of oxide magnetic plates which are generally flat; an underlying layer formation step of forming at least one underlying layer on each of the pair of oxide magnetic plates; a metal magnetic thin film formation step of forming the metal magnetic thin film on the underlying layer, the metal magnetic thin film being formed using a solid material containing an element which is a main component of the metal magnetic thin film in an atmosphere containing at least one of oxygen and nitrogen by a gas phase technique; a track formation step of forming a groove in a body including the oxide magnetic plate, the underlying layer, and the metal magnetic thin film so that the groove has a width corresponding to a track; and a combining step of combining the body with another body including an oxide magnetic plate, an underlying layer, and a metal magnetic thin film, with the nonmagnetic layer interposed therebetween.
In one embodiment of the invention, the steps are performed in the order of the winding window formation step, the underlying layer formation step, the metal magnetic thin film formation step, the track formation step, and then the combining step.
In one embodiment of the invention, the steps are performed in the order of the underlying layer formation step, the metal magnetic thin film formation step, the winding window formation step, the track formation step, and then the combining step.
According to still another aspect of the invention, a video recording and reproduction apparatus includes a cylinder having any of the above-defined magnetic heads mounted thereon; a head/tape interface mechanism for winding a magnetic tape around the cylinder; a cylinder driving section for driving the cylinder; and a magnetic tape driving section for driving the magnetic tape wound around the cylinder.
According to still another aspect of the invention, a video camera includes a cylinder having any of the above-defined magnetic heads; a head/tape interface mechanism for winding a magnetic tape around the cylinder; a cylinder driving section for driving the cylinder; a magnetic tape driving section for driving the magnetic tape wound around the cylinder; an optical system for converting a video signal into an electric signal; and a signal processing circuit for outputting the electric signal obtained by conversion by the optical system to the magnetic head.
Thus, the invention described herein makes possible the advantages of providing a magnetic head which (i) is satisfactory in the anti-corrosion characteristic and an input and output characteristic and is sufficiently durable against cracking in a base and (ii) has an optimum combination of a metal magnetic thin film and a head structure; a method for producing the magnetic head; a video recording and reproduction apparatus including the magnetic head; and a video camera including the magnetic head.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.